118 BATHYMETRICAL SURVEY OF 



were recorded, surrounded in each case by deeper water. These shallow 

 soundings mark the position of a rocky ridge, said to cross the loch, and 

 to be a continuation of the rocky ridge on the east shore, now used as a 

 quarry. About midway along the eastern shore there is a slight con- 

 striction in the outline of the loch at the entrance of the Allt Bhaltair, 

 apparently due to the material brought down by that stream, and in 

 this position a slight shoaling of the bottom in the centre of the loch is 

 observable, the depth being 73 feet, with two soundings of 77 feet to the 

 north, and soundings of 77 and 79 feet to the south. The 2 5 -feet basin 

 is about three-quarters of a mile in length, approaching to within 100 

 feet from the northern end, and a quarter of a mile from the southern 

 end. The slope of the bottom is steeper off the western than off the 

 eastern shore; near the middle of the western shore a sounding of 40 

 feet was taken about 50 feet offshore, giving a gradient of 1 in 1-25. 

 The area of the lake-floor covered by less than 25 feet of water is about 

 85 acres, or 52 per cent, of the total area of the loch ; that covered by 

 water between 25 and 50 feet in depth is about 36 acres, or 22 per 

 cent. ; that covered by water between 50 and 75 feet in depth is about 

 36 acres, or 22 per cent. ; and that covered by more than 75 feet of 

 water is about 7 acres, or 4 per cent, of the entire area of the loch. 

 The flat-bottomed character of the deep basin is well brought out by the 

 fact that the area between the 25- and 50-feet contour-lines is almost 

 identical with the area between the 50- and 75 -feet contours. Loch 

 Turret was surveyed on June 9, 1903, and the elevation of the lake 

 surface above the sea, measured from the spot-level 1145 on the east 

 shore, was determined as being 1132 feet. The water in the loch was 

 high on the date of the survey. 



Temperature Observations. The temperature of the surface water 

 on commencing the survey at 9 a.m. was 60'0, and a series of tem- 

 peratures taken later in the deepest part of the loch gave the following 

 results : 



Surface ... 60 8 Fahr. 



10 feet ... 59-o ,, 



15 54-0 



25 477 



~>0 44-8 ,, 



75 44 -4 ,, 



This series shows a range of temperature from surface to bottom 

 amounting to 16-4, there being a fall of 5-0 between 10 and 15 feet, 

 one of 6-3 between 15 and 25 feet, and one of 3 between 25 and 50 

 feet; the decrease of temperature between 10 and 15 feet was thus 

 equal to 1 per foot of depth. 



Lochan Uaint (see Plate XXXII.). Lochan Uaine, at the head of 

 Glen Turret, lies in a corrie; its shores are peat, and the bottom weedy. 





